In a combustion region formed inside a combustion cylinder of a gas-turbine combustor, pressure fluctuations are generated by flames, those pressure fluctuations propagate (feed back) to a gas-turbine combustion burner, the flow rate of fuel sprayed (ejected) into the combustion region from fuel spraying holes in the gas-turbine combustion burner fluctuates, and that flow-rate fluctuation propagates to the flames, aggravating the pressure fluctuations.
Therefore, one known way to suppress the pressure fluctuations in the combustion region is to use an acoustic liner disclosed, for example, in Patent Literature 1.